Friction stir welding (FSW) is an innovative solid state joining technique and has been employed in industries for joining aluminum, magnesium, zinc and copper alloys. The FSW process parameters such as tool, rotational speed, welding speed, axial force, etc play major role in deciding the weld quality. A mathematical modeling was developed based on experiments to predict the tensile strength of dissimilar FSW aluminum alloys. The maximum tensile strength of 210 MPa can be obtained at the tool rotational speed of 1100 rpm, welding speed of 35mm/min and an axial load of 7 kN is the Optimum welding parameters.